ADE7758ARWZ Analog Devices Inc, ADE7758ARWZ Datasheet - Page 46

• Manufacturer Part Number: ADE7758ARWZ
• Description: IC ENERGY METERING 3PHASE 24SOIC
• Manufacturer: Analog Devices Inc

Specifications of ADE7758ARWZ

• Input Impedance: 380 KOhm
• Measurement Error: 0.1%
• Voltage - I/o High: 2.4V
• Voltage - I/o Low: 0.8V
• Current - Supply: 8mA
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (0.300", 7.50mm Width)
• Meter Type: 3 Phase
• Ic Function: Poly Phase Multifunction Energy Metering IC
• Supply Voltage Range: 4.75V To 5.25V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: SOIC
• No. Of Pins: 24
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADE7758
Phase Calibration Using Pulse Output
The ADE7758 includes a phase calibration register on each phase
to compensate for small phase errors. Large phase errors should
be compensated by adjusting the antialiasing filters. The ADE7758’s
phase calibration is a time delay with different weights in the
positive and negative direction (see the Phase Compensation
section). Because a current transformer is a source of phase error,
a fixed nominal value can be decided on to load into the xPHCAL
registers at power-up. During calibration, this value can be adjusted
for CT-to-CT error. Figure 78 shows the steps involved in
calibrating the phase using the pulse output.
Step 1: Step 1 and Step 3 from the gain calibration should be
repeated to configure the ADE7758 pulse output. Ensure the
xPHCAL registers are zero.
Step 2: Set the test system for I
inductive.
Step 3: Measure the percent error in the pulse output, APCF,
from the reference meter using Equation 49.
Step 4: Calculate the Phase Error in degrees by
FOR LINE PERIOD
FREQ[11:0] FOR A
SELECT PHASE
MEASUREMENT
MEASUREMENT
LINE PERIOD
CONFIGURE
AWG
Phase
END
YES
=
Error
Figure 78. Phase Calibration Using Pulse Output
–
. 0
. 5
PHASE ERROR
( )
0244
CALIBRATED?
°
26
PHASES
START
=
%
ALL
–
%
PERIOD USING
FREQ[11:0]
Arcsin
MEASURE
REGISTER
=
−
215
⎛
⎜
⎝
TEST
NO
NO
100
5 .
%Error
PF = 0.5, INDUCTIVE
CALCULATE PHASE
, V
STEP 1
STEP 2
STEP 3
STEP 4
ERROR (DEGREES)
PHASE A, B, OR C
=
AND ENABLE CF
FOR I
SET UP SYSTEM
ERROR IN APCF
%
SET UP PULSE
OUTPUT FOR
MEASURE %
−
NOM
PERIOD OF
OUTPUTS
×
KNOWN?
216
SYSTEM
TEST
, and 0.5 power factor
3
, V
=
⎞
⎟
⎠
NOM
0
xF
,
CALCULATE AND
STEP 5
28
YES
WRITE TO
xPHCAL
(53)
Rev. D | Page 46 of 72
Step 5: Calculate xPHCAL.
where PHCAL_LSB_Weight is 1.2 μs if the %Error is negative or
2.4 μs if the %Error is positive (see the Phase Compensation
section).
If it is not known, the line period is available in the ADE7758’s
frequency register, FREQ (0x10). To configure line period
measurement, select the phase for period measurement in the
MMODE[1:0] and set LCYCMODE[7]. Equation 55 shows how
to determine the value that needs to be written to xPHCAL
using the period register measurement.
Example: Phase Calibration of Phase A Using Pulse Output
For this example, I
I
0.5 inductive, and Frequency = 50 Hz.
With Phase A contributing to CF, at I
inductive power factor, the example ADE7758 meter shows
0.9668 Hz on the pulse output. This is equivalent to −1.122%
error from the reference meter value using Equation 49.
The Phase Error in degrees using Equation 53 is 0.3713°.
If at 50 Hz the FREQ register = 2083d, the value that should be
written to APHCAL is 17d, or 0x11 using Equation 55. Note
that a PHCAL_LSB_Weight of 1.2 μs is used because the
%Error is negative.
Power Offset Calibration Using Pulse Output
Power offset calibration should be used for outstanding
performance over a wide dynamic range (1000:1). Calibration
of the power offset is done at or close to the minimum current
where the desired accuracy is required.
The ADE7758 has power offset registers for watts and VAR
(xWATTOS and xVAROS). Offsets in the VA measurement are
compensated by adjusting the rms offset registers (see the
Calibration of IRMS and VRMS Offset section). Figure 79
shows the steps to calibrate the power offsets using the pulse
outputs.
FULLSCALE
xPHCAL
Phase
Phase
Phase
xPHCAL
APHCAL
= 130 A, MC = 3200 impulses/kWh, Power Factor =
Error
Error
Error
=
=
×
=
PHCAL
( )
. 0
×
°
TEST
3713
PHCAL
=
– Arcsin
= 10 A, V
× °
_
LSB
1
9
_
1
9
2 .
6 .
6 .
LSB
⎛
⎜
⎝
μs
μs
_
μ
100
NOM
–
Weight
s
×
_
1.122%
Weight
%
2083
360
= 220 V, V
×
TEST
°
×
3
, V
=
17
Line
⎞
⎟
⎠
×
NOM
=
FREQ
.
19
. 0
FULLSCALE
, and 0.5
Period
3713
=
360
1
17
[
11
°
°
=
(
:
s
0
] 0
= 500 V,
)
x
×
11
360
1
(55)
°
(54)